Structural engineering

Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design the 'bones and muscles' that create the form and shape of human-made structures. Structural engineers also must understand and calculate the stability, strength, rigidity and earthquake-susceptibility of built structures for buildings and nonbuilding structures. The structural designs are integrated with those of other designers such as architects and building services engineer and often supervise the construction of projects by contractors on site. They can also be involved in the design of machinery, medical equipment, and vehicles where structural integrity affects functioning and safety. See glossary of structural engineering. Structural engineering theory is based upon applied physical laws and empirical knowledge of the structural performance of different materials and geometries. Structural engineering design uses a number of relatively si

Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

Kyriaki Goulouti

The thermal bridges constitute critical regions in building envelopes and they are created due to the interruption of the insulation layer. One of the many structural thermal bridges in building envelopes is created in balcony junctions because of the required structural continuity of the concrete slab. The detrimental effects of such thermal bridges are minimized, by using thermal breaks that interrupt the heat flow towards the external environment by adding an intermediate insulation layer between the internal floor and the balcony slab. For the majority of these thermal breaks, the load transfer from the balconyâs cantilever to the main structure occurs through stainless steel bars, which penetrate the insulation layer and still have a high thermal conductivity. The current research proposes a new thermal break composed of fiber-reinforced polymer composite materials (FRP) that have much better thermal properties than the conventional materials and investigates its short- and long-term structural and thermal behavior. The tensile force from the cantilever moment is transmitted by an aramid-FRP (ARFP) loop, whose thermal conductivity is about 170 times smaller than that of stainless steel. The compression component of the moment is transferred by a short glass-FRP (GFRP) element while the shear compression diagonal is transmitted by a FRP-PU hexagonal foam sandwich. The insulation layer is composed of a thin layer of aerogel granulate. All the components are assembled in a polymer box. The thermal performance of the above-mentioned thermal break was validated by estimating its impact on the energy balance of a traditional building, using three different building envelopes (a MINERGIE envelope, a MINERGIE-P envelope and an optimum envelope). Furthermore, 3d finite element steady-state thermal simulations were performed in order to define the true losses through the optimized thermal break. Finally, the thermal behavior of the thermal break was compared with that of traditional thermal breaks. The structural validation of the FRP thermal break included the mechanical characterization of the components through static, long-term and durability experiments. The static experiments of the components comprised tensile experiments (AFRP loop) and compression experiments (FRP-PU hexagonal foam sandwich and GFRP bar). The long-term behavior was evaluated through tensile and compression creep experiments, while its simulation and prediction were achieved by applying traditional creep methods and two new proposed models that were able to predict the secondary creep stage (Gradient regression and Gradient regression with NHPP). The durability was evaluated by their immersion in alkaline environment, simulating that of the concrete. Finally, the total behavior of the balcony junction was examined through full scale beam experiments that led to the analytical modelling of the system.

EPFL2016

Local structural effects in fiber-reinforced polymer web-core sandwich structures

Sonia Yanes Armas

Glass fiber-reinforced polymer (GFRP) pultruded decks and sandwich panels currently represent two of the most extensive applications of FRP materials for load-bearing structural components in the bridge and building domains. Based on the state of the art, the global structural behavior of both systems has been fairly well investigated. Nonetheless, local effects governing in most cases the global behavior have been barely addressed. Selected local structural effects relevant to the global structural performance of pultruded GFRP bridge decks and GFRP-foam web-core sandwich structures are therefore investigated in this research. The effect of the core geometry of pultruded GFRP decks on the systemâs behavior in its transverse-to-pultrusion direction was experimentally investigated. The experimental work conducted on two deck designs with trapezoidal- and triangular-cell cross sections showed that the transverse structural performance depends on the cell geometry. Furthermore, the systemsâ transverse bending and in-plane shear stiffness were evaluated and the results indicated that a triangular core causes a more pronounced bi-directional behavior of the deck when it is subjected to concentrated loads. The local behavior of the web-flange junctions (WFJs) of the pultruded deck with trapezoidal cells was experimentally investigated regarding energy dissipation capacity and recovery subsequent to unloading. The experimental responses reported for two junction types with similar geometry and fiber architecture but different initial imperfections demonstrated that dissimilar imperfections could significantly affect WFJ behavior and change it from brittle to ductile. The time-dependent recovery and energy dissipation mechanisms of the WFJs exhibiting a ductile response were evaluated; the viscoelastic effects were found to be small in both cases. The rotational behavior of all WFJ types present in the trapezoidal-core deck was characterized. An experimental procedure based on three-point bending and cantilever experiments conducted on the web elements was developed and used for this purpose. The rotational stiffness, strength and failure modes of the WFJs differed depending on the web type, location of the WFJ within the deck profile, existing initial imperfections and direction of the applied bending moment. Numerical simulations of the full-scale deck were performed to demonstrate the validity of the experimental moment-rotation (M-Ï) relationships and simplified M-Ï curves provided. The effects of creep on the load-bearing behavior of GFRP-foam web-core sandwich structures were investigated. A study of the creep behavior of polyurethane (PUR) foams was conducted and showed that in order to assess the long-term structural performance of the sandwich system, the foam anisotropy, density and loading type should be considered. The creep behavior of web-core sandwich panels, and specifically the structural aspects affected by the web-core interaction, were analyzed using the GFRP-PUR sandwich roof of the Novartis Campus Main Gate Building as case study and currently available design guidelines. The resulting sandwich designs depended on the applied design recommendations. Finally, provisions for the cross-sectional design of the hybrid web-core were proposed.

EPFL2017

Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

Kyriaki Goulouti

EPFL2016

Local structural effects in fiber-reinforced polymer web-core sandwich structures

Sonia Yanes Armas

EPFL2017

Structural design and optimization of FRP curved sandwich panels used as the enclosure structure of a large bridge

Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

Local structural effects in fiber-reinforced polymer web-core sandwich structures

Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

Local structural effects in fiber-reinforced polymer web-core sandwich structures

Structural design and optimization of FRP curved sandwich panels used as the enclosure structure of a large bridge